Foot prosthesis having auxiliary ankle construction

ABSTRACT

A prosthetic foot characterized by a foot portion having an ankle portion demountably and interchangeably connected thereto. The foot portion and ankle portion are fabricated from polymer impregnated and encapsulated laminates, including such laminates as carbon fibers and/or fiberglass or synthetic fibers such as Kevlar. The demountable connection of the ankle portion permits interchangeability of ankle and foot portions to match the weight, stride and activity schedule of the wearer utilizing the prosthetic foot. Auxiliary ankle members and wedge blocks between the foot portion and the ankle portion provide additional adjustability. A split sleeve is provided for assembling the various components.

BACKGROUND OF THE INVENTION

This invention relates to foot prostheses in general, and specificallyto a prosthetic foot characterized by a unitary foot and heelconstruction, and/or an auxiliary ankle construction which permits theflexibility of the prosthesis to be selectively determined and easilychanged. The invention also includes an improved coupling for attachingsaid foot prosthesis to an auxiliary pylon tube.

The prior art is replete with various types of mechanical devicespurporting to solve the foot prosthesis problem. Typical of earlydevices is Lange U.S. Pat. No. 2,075,583, which incorporates a rubberform mounted in operative relationship with a rigid metallic core.Exemplary of the latest developments in the field is Poggi U.S. Pat. No.4,645,509, which teaches a prosthetic foot incorporating a monolithickeel or beam of relatively massive proportions intended to react to theload of an amputee's body during walking, running, jumping, and the likeand to release the resultant stored energy to create foot lift andthrust complementing the amputee's natural stride.

However, each of the prior art devices has significant deficiencies;specifically, the component parts of the prosthesis, as in Lange, aretoo heavy and too rigid or, as in Poggi, are too massive and monolithicto respond properly to the nuances of stress-response gradientscharacteristic of the human foot.

One of the primary factors which has inhibited the creation of a trulysuccessful prosthetic foot has been the fixation of the prior art withthe duplication of the structural aspects of the skeletal and muscularcomponents of an actual human foot. In many instances, as exemplified byPoggi '509 mentioned hereinabove even the toes of the foot are attemptedto be duplicated by providing simulacra thereof. It is this fixationupon the mechanical elements of the human foot which has restricted theart to an attempt to duplicate the human foot components, a tendencywhich is particularly exemplified in Gajdos U.S. Pat. No. 3,335,428.

My copending application Ser. No. 07/293,824, now U.S. Pat. No. 5,037,44discloses certain concepts relating to a prosthetic foot characterizedby a forefoot portion and a heel portion which may be permanently ordemountably associated with each other whereby both the forefoot portionand the heel portion can be readily exchanged with correspondinglyconstructed heel and forefoot portions. This exchangeability permitssize adjustment or accommodation of different spring rates to suit thesize of foot of the amputee or the stride and weight of the amputee,yielding an almost infinite range of combinations of spring rate andsize to the amputee, and allowing a natural stride and resilience ofgait which has not been obtainable by prior art prosthetic devices.Other than my present invention and my copending application, I amunaware of any prosthetic foot device incorporating such demountablyattached forefoot and heel portions, and providing such ease and rangeof adjustability.

OBJECTS AND ADVANTAGES OF THE INVENTION

It is, therefore, an object of my invention to provide a foot prosthesiswhich is characterized by a foot portion and an ankle portion which maybe permanently or demountably associated with each other, with the ankleportion having an upwardly extending attachment section providing easeof manufacture and resistance to rotation, whereby both the foot portionand the ankle portion can be readily exchanged with correspondinglyconstructed foot and ankle portions to provide size adjustment oraccommodation of different spring rates to suit the size of foot of theamputee or the stride and weight of the amputee, and further adjustmentscan be made by the use of an auxiliary ankle spring member. Therefore,an almost infinite combination of spring rate and size can be providedto the amputee, achieving a natural stride and resilience of gait, whichhas not been obtainable by prior art prosthetic devices.

Another object of the invention is the provision in a prosthetic foot ofthe aforementioned character of an interchangeable or permanent footportion which has a toe section, an arch section, and a heel section,all constructed without the necessity of tapering of the thicknessthereof. Also incorporated in the aforementioned foot is an ankleportion which incorporates an upper attachment section, a curvilinearankle section, and a lower attachment section secured to theintersection of the arch and toe sections of the foot portion. Thepreviously mentioned heel section of the foot portion extends beyond thecurvilinear ankle and attachment sections of the ankle portion.

As previously indicated, the ankle portion can be provided in differentsizes and spring rates, and an auxiliary ankle member may be utilized,thus permitting the gait, weight, and activity level of the amputee tobe readily accommodated. Correspondingly, the ankle portion can bedemountably associated with the foot portion of the foot to permitdifferent sizes of foot portion having different spring rates to bemounted in operative relationship with the ankle portion.

Another object of the invention is the provision of a prosthetic foot ofthe aforementioned character in which both the foot and ankle portionsof the foot are fabricated, and the auxiliary ankle may be fabricated,from superimposed laminates maintained in operative relationship by anencapsulating polymer, and further in which said toe, arch and heelsections of said foot portion, said spring section of said ankleportion, and said auxiliary ankle attachment are susceptible to bendingstress determined by the number of the laminates and polymers in therespective toe, arch and heel sections of said foot portion, in saidspring section of said ankle portion, and in said auxiliary ankleattachment. Thus, the various portions and sections thereof areencapsulated in a polymer and capable of spring stress response as ankleloads are imposed thereupon during the utilization of said foot.

A further object of the invention is the provision, in a prosthetic footof the aforementioned character, of a foot portion which consists ofcontinuous, integrally and simultaneously formed toe, arch, and heelsections, said sections being fabricated as a unitary structure bypolymer impregnation of superimposed reinforcing laminae maintained inthe desired configuration of said foot portion and said toe, arch andheel sections being capable of spring stress generated energy storagewhereby the subjection of the toe or heel sections to bending momentswill cause uniform transmission of spring stress through said archsection and through said curvilinear ankle section of said ankle portionto said attachment section thereof.

Another object of the invention is the provision of the aforesaidprosthetic foot in which the ankle section of said ankle portion has itsupper extremity constituted by said upper attachment section and itslower extremity extending into and constituting said lower attachmentsection, said lower extremity, said curvilinear ankle section and saidupper attachment section maintaining an approximately uniform thicknesstransversely of the longitudinal axis of said sections. Similarly, saidfoot portion and its various sections are provided with an approximatelyuniform thickness transversely of the longitudinal axis of saidsections.

A further object of the invention is the provision of the aforesaidauxiliary ankle attachment, which is associated with the ankle sectionof said ankle portion to increase the resistance of said ankle sectionto loads imposed upon the toe section of said foot portion. The conceptof the auxiliary ankle involves the provision of ankle memberscharacterized by different spring rates, which permits the resistance ofthe ankle section to deflection to be precisely adjusted to the weight,activity level and other characteristics of the individual for whom saidfoot is being adjusted.

The polymers utilized to encapsulate the fibrous laminae arecharacterized by elasticity and flexibility so that the foot and ankleportions deflect proportionally to the engagement of said foot portionwith an adjacent surface, causing the resultant energy to be stored andsubsequently released when the gait of the amputee incorporating thrustand lift components results in the utilization of the stored energy anda consequent reduction of the energy expended by the amputee. There is agradual increase in stiffness as the lever arm of the toe section of thefoot portion shortens due to gradual deflection thereof.

It is an additional object of my invention to provide an improvedcoupling mechanism for attaching a prosthetic foot of the abovementionedcharacter to an auxiliary pylon tube which is in turn attached to thewearer's leg.

Another object of the invention is the provision in a prosthetic foot ofthe aforementioned character of a forefoot portion which incorporates anupwardly extending attachment section, a curvilinear ankle section, anarch section and a toe section. As previously mentioned, the forefootportion can be provided in different sizes and spring rates, and anauxiliary ankle member may be utilized, thus permitting the gait,weight, and size of foot of the amputee to be readily accommodated. Alsoincorporated in the aforementioned foot is an interchangeable orpermanent heel portion which has an attachment section secured to theintersection of the arch and toe sections of the forefoot portion and aheel section extending beyond the curvilinear ankle and attachmentsections of the forefoot portion.

In order to impart a cosmetic aspect to the prosthetic foot, afterproper fitting of the foot to insure that the foot and ankle portionsand the auxiliary ankle are properly balanced and of appropriate size,the prosthesis may be encapsulated in a suitably shaped foot-like shroudto facilitate the utilization of the prosthetic foot with a conventionalshoe. The enclosure must be sufficiently flexible so as not to inhibitthe free movement and flexure of the foot and ankle portions and theauxiliary ankle of the prosthetic foot, but, because of the inherentlyresilient and stress-absorbing characteristics of said foot, littledependence is needed upon the ancillary cushioning action of theenclosure.

Consequently, the foot of my invention is characterized by extreme lightweight, instantaneous response to imposed loads and correspondinglyinstantaneous delivery of stored energy when the gait of the wearerindicates that such stored energy is to be released. Moreover, the footmay be readily mounted in operative relationship with conventionalancillary pylons and couplings, and can be fine-tuned by the blending ofthe foot and ankle portions and auxiliary ankle characteristics toachieve the ultimate in operative response to the needs of the wearer.

Consequently, the wearer of the foot may engage in a wide variety ofactivities which were precluded in the past because of the structurallimitations and corresponding performances of prior art prostheses.Running, jumping and other activities are sustained by the foot and itmay be utilized in the same manner as the normal foot of the wearer.

Other objects and advantages of the invention will be apparent from thefollowing specification and the accompanying drawings, which are for thepurpose of illustration only.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a side elevation view of portion of a prosthesis constructedin accordance with the teachings of the invention;

FIG. 2 is a partially sectional plan view, taken along line 2--2 of FIG.1;

FIG. 3 is a front elevation view, taken along line 3--3 of FIG. 2; and

FIG. 4 is a partially sectional side elevation view, taken along line4--4 of FIG. 2.

FIG. 5 is a side elevation view of portion of an alternative embodimentof a prosthesis constructed in accordance with the teachings of theinvention;

FIG. 6 is a partially sectional plan view, taken along line 6--6 of FIG.5;

FIG. 7 is a front elevation view, taken along line 7--7 of FIG. 6; and

FIG. 8 is a partially sectional side elevation view, taken along line8--8 of FIG. 6.

DESCRIPTION OF PREFERRED EMBODIMENT OF THE INVENTION

Referring to the drawings, and particularly to FIGS. 1 and 2 thereof, Ishow a foot prosthesis 10 constructed in accordance with the teachingsof the invention and including a foot portion 12 and an ankle portion 14operatively and demountably connected to each other by bolt and nutcombinations 16 associated with loadtransmitting metallic plates 17. Ifindicated, the foot and ankle portions can be permanently secured toeach other, as by epoxy adhesive, an intermediate resilient member, orthe like.

The ankle portion 14 of the prosthesis 10 includes a substantially rigidupper attachment section 18, FIG. 4, a curvilinear ankle section 20, anda lower attachment section 22. The sections 18, 20, and 22 of the ankleportion 14 are formed integrally with one another and simultaneously bya plurality of Juxtaposed, shaped laminae embedded in a hardened,flexible polymer.

The attachment section 18 has a rearward surface 58, as shown in FIG. 4,and a forward surface substantially parallel thereto. The attachmentsection 18 is substantially rigid and capable of sustaining torsional,impact and other loads impressed thereupon by the foot portion 12 andankle portion 14 of the prosthesis 10. In addition, the inherentrigidity of the attachment section 18 prevents it from being distortedin any way and causes the effective transmission of the aforesaid loadsimposed thereupon to a suitable ancillary prosthetic pylon 30, through apylon coupling 32, constructed of graphite or some other appropriatelystrong material.

The pylon coupling 32 incorporates a split sleeve 34 which surrounds theattachment section 18, an auxiliary ankle member 50 (if any, as morethoroughly described below), and the prosthetic pylon 30. Tab members 36are provided at the split in sleeve 34, and said tab members areprovided with two centrally located openings 38, FIG. 4, adapted toaccommodate bolt and nut combinations 40. The bolt and nut combinations40 can be tightened to cause the pylon coupling 32 to grip and cause africtional engagement of the attachment section 18, the auxiliary anklemember 50, if any, and the prosthetic pylon 30.

The pylon coupling 32 further includes gripping means 42, shown in thepreferred embodiment as angular projections located on the internalsurface of the coupling 32 in the interstices between the ancillaryprosthetic pylon 30 and the attachment section 18 or the auxiliary anklemember 50, if any. Gripping means 42 are so sized and shaped as toprovide additional surface contact and improve the aforementionedfrictional engagement between the coupling 32, the pylon 30, and theattachment section 18 or the auxiliary ankle member 50 if present.

As shown in the drawings of the preferred embodiment, the tab members 36associated with the split in the coupling 32 are adjacent the front ofthe prosthetic pylon 30, but those skilled in the art will understandthat the aforementioned split and the tab members 36 associatedtherewith may alternatively be oriented toward the side or rear of theprosthetic foot 10, and still be within the scope of the presentinvention.

As previously mentioned, an auxiliary ankle member 50 can be utilized todecrease the flexibility of the ankle portion 14. The auxiliary ankle 50is formed from fibrous laminates of the same character as the variousportions of the prosthesis 10. In the preferred embodiment, theauxiliary ankle 50 incorporates an attachment section 44 which ismounted inside the coupling 32, between the ancillary pylon 30 and theattachment section 18 of the ankle portion 14. The auxiliary ankle 50 issecured in operative relationship with the curvilinear ankle section 20of ankle portion 14 through the aforementioned assembly of the coupling32, which retains the various components in the aforesaid operativerelationship. On its end opposite the attachment section 44, anklemember 50 has a tapered section 46 which provides a varying flexibilityalong the length of the ankle member 50 and also lessens the likelihoodthat the ankle member 50 will be undesirably snagged or restrained inits cooperative relationship with ankle portion 14 and the cosmeticcover of the prosthesis, more thoroughly discussed below. In alterativeembodiments, as will be understood by those skilled in the art, suchtapering is not required in order to practice the invention, andaccordingly, the ankle member 50 can be provided with a relativelyuniform thickness along the length thereof.

In the preferred embodiment, the auxiliary ankle member 50 is securedagainst the internal radius of the curvilinear ankle section 20, so thatthe anticipated upward deflection of a toe section 24 of the footportion 12, as more thoroughly described below, will eventually causedeformation of the auxiliary ankle 50 as well as deformation of theankle section 20, effectively combining the deformation resistance andenergy storage characteristics of the auxiliary ankle member 50 withthose of the ankle section 20. Alternative embodiments would includesecuring the auxiliary ankle 50 to the rearward surface 58 of theattachment section 18 and further securing the auxiliary ankle taperedsection 46 to an under surface 62 of the ankle section 20 in order toachieve the aforedescribed desired combination of the deformationresistance and energy storage characteristics of the auxiliary anklemember 50 with those of the ankle section 20.

The auxiliary ankle member 50 can be provided with different numbers oflaminates to make it more or less compliant to loads transmitted throughthe ankle section 20. Consequently, when confronted with variousanomalies in an amputee, such as overweight or excess activity levels,the basic structure of the ankle portion 14, and more particularly theankle section 20, can be materially modified to provide ankle portionaction which is precisely adjusted to the needs of the amputee.Moreover, a variety of auxiliary ankle members 50 can be made availableto an amputee, allowing the flexibility of the prosthesis to be adjustedon the basis of the particular activity which the amputee isundertaking.

As previously mentioned, a cosmetic cover, not shown, can be provided toshroud the prosthesis 10 after the optimum assemblage of the foot andankle portions 12 and 14 and any auxiliary ankle member 50 has beenaccomplished. Unlike prior art constructions, however, the cosmeticcover, which may be formed of low-density formed polymer, is notrequired to serve any ancillary shock-absorbing or otherstress-isolating function since all of the loads imposed upon theprosthesis can be absorbed, transmitted and reasserted in a manner to bedescribed in greater detail below.

The bolt and nut combinations 16, in conjunction with theload-distributing metallic plates 17, serve to secure the ankle portion14 in operative relationship with the foot portion 12 of the prosthesis10, as best shown in FIGS. 1-2 of the drawings. The aforesaid mode ofaffixation facilitates the assembly or dismounting of selected ankleportions 14 in operative relationship with selected foot portions 12 ofthe prosthesis 10, thus permitting a wide range of different sizes andstress load response characteristics to be related to each other toaccomplish the optimum functional correspondence between the foot andankle portions 12 and 14 to accommodate to the maximum extent the needsof the wearer of the prosthesis, and, also, to provide for a propermating of the prosthesis 10 with a selected, ancillary pylon 30 or thelike.

The foot portion 12, as best shown in FIG. 1 of the drawings, includes atoe section 24, an arch section 26, and a heel section 28 which has itsrearward extremity 56 extending beyond the extreme rearward surface 58of the ankle portion attachment section 18 of the prosthesis 10. Matingbores, not shown, in the arch section 26 of the foot portion 12 and theankle portion 14 receive the respective bolt and nut combinations 16 toprovide for the aforesaid facility in assembling and disassembling ofthe foot and ankle portions 12 and 14. In the preferred embodiment, thevarious sections of the foot portion 12 are all constructed without thenecessity of tapering of the thickness thereof, although those skilledin the art will understand that the invention is not limited to suchnon-tapering construction.

Interposed between the under surface 62 of the ankle section 20 of theankle portion 14 and an upper surface 64 of the heel section 28 is aresilient, spring action function block 70 of wedge-shaped configurationto determine the lever arm of the heel section 28 and isolate the undersurface 62 of the ankle section 20 and the upper surface 64 of the heelsection 28 from each other. The function block 70 may be fabricated froma wide variety of resilient materials, including natural and syntheticrubbers, or the like.

Similarly, a second spring action function block 72 of like shape andconstruction can be interposed between an under surface 74 of the lowerattachment section 22 of the ankle portion 14 and an upper surface 76 ofthe toe section 24 to determine the lever arm of the toe section 24 andisolate the under surface 74 of the lower attachment section 22 and theupper surface 76 of the toe section 24 from each other.

The materials from which the foot portion 12 and ankle portion 14 andthe auxiliary ankle 50 are fabricated must be such as to provide anenergy-storing, resilient, spring-like effect. This is necessary becauseeach engagement of the prosthesis 10 with an adjacent surface impressescompression, torsional and other loads upon the prosthesis 10 which mustbe stored within the prosthesis and then, dependent upon the stride ofthe wearer, be reimpressed upon said surface to achieve a natural strideconforming, ideally, in all respects to the stride of the unimpairedlimb of the wearer of the prosthesis 10.

The foot and ankle portions 12 and 14 and the auxiliary ankle 50 of theprosthesis are preferably molded as unitary components and are carefullyformed to provide for uniform absorption of stress imposed thereupon.The configuration of both portions 12 and 14 is of utmost importance andthe laminates and the polymer or polymers from which the portions 12 and14 are fabricated must be resilient and capable of absorbing thecompressive, torsional and other stresses referred to hereinabove and ofrestoring the stored energy created by such stresses, in a naturalmanner, to the impacted surface which originally imposed such stressesupon the prosthesis 10.

It has been found that there is a limited number of polymers capable ofsustaining the significant stresses and repetitive loads imposed uponthe prosthesis 10, particularly in the light of the countless numbers ofcycles to which the prosthesis 10 is subjected during normal, everydayuse.

At present, the best materials for the prosthesis are a composite ofhigh-strength graphite fiber in a high-toughness epoxy thermosettingresin system. There are several reasons for this: (1) high strength; (2)stiffness to weight ratio of graphite as compared to other materials;(3) the almost complete return of input or stored energy; (4) lightweight; (5) high fatigue strength; and (6) minimal creep. As analternative material, fiberglass/epoxy is a fair choice, but it is notas good as graphite because of lower fatigue strength and higherdensity. Kevlar is even less acceptable due to poor compression andshear strength, although it is the lowest density of those mentioned.

An important aspect of the polymers and laminates referred tohereinabove is that they are characterized by needed, but not excessive,flexural deflection under load, which characteristic permits theshock-absorption stress loading of the prosthesis 10 while maintainingsufficient stability to prevent the collapse of the foot and ankleportions 12 and 14 and the ankle member 50 of the prosthesis 10 whileloads are imposed thereupon.

To achieve the relatively thin construction of the foot and ankleportions 12 and 14 and the auxiliary ankle member 50 of the prosthesis10, the aforesaid polymers are utilized in conjunction with variouslaminating materials. Various types of fibrous laminae can be utilizedto achieve the continuum required by the design of the foot and ankleportions 12 and 14 and the ankle member 50 to complement thestress-absorbing and storing characteristics of the polymers in whichsaid fibrous laminae are embedded.

Of course, there is a wide variety of fibrous reinforcements in the formof laminae available at the present time, including such inorganicfibers as glass or carbon fibers. These inorganic fibers are customarilyprovided in tape or sheet form and can be readily superimposed in themold to permit them to be encapsulated in the selected polymer.

Obviously, the number of superimposed laminae and the lengths thereof,together with the thickness of the encapsulating polymer, determine thestress characteristics of the resultant foot and ankle portions 12 and14 and the ankle member 50 and, correspondingly, determine the totalweight of the prosthesis 10. As will be apparent from the discussionhereinbelow, the individual foot and ankle portions 12 and 14 and anklemember 50 are designed to specifically accommodate individuals havingdifferent foot sizes, different weights and different strides and theindividual design of the foot and ankle portions 12 and 14 and the anklemember 50 provides for matching, to an extent previously unknown in theart, the natural characteristics of the wearer's uninjured limb.

Furthermore, the function blocks 70 and 72 can be provided in differentsizes and in materials having different compression characteristics sothat the respective lever arms and the corresponding deflections of theheel section 28 and the toe section 24 may be increased or decreased.

As previously mentioned, the ankle section 20 is formed integrally withthe upper attachment section 18 and said attachment section constitutesthe upper extremity of the ankle section 20, while the initiation of thelower attachment section 22 of the ankle portion 12 constitutes thelower extremity of the ankle section 20. The configuration of the anklesection 20, in conjunction with the auxiliary ankle member 50, is themeans whereby compressive loads imposed during impingement of the footand ankle portions 12 and 14 upon an adjacent surface are absorbed andsubsequently reimposed upon said surface The ankle portion 20 and theauxiliary ankle member 50 are so designed that they function,substantially, as an ankle joint to permit pivoting of the foot portion12 thereabout in a manner analogous to the manner in which the normalfoot pivots about the normal ankle joint on an axis transversely of saidankle joint.

The radii of curvature of the ankle section 20 and any auxiliary anklemember 50 correspond to provide for the inherent resilience anddeflection of the foot portion 12 while inhibiting undesired, excessivecollapse of the ankle section 20.

It will be noted that the arch section 26 of the foot portion 12 issubstantially rigid and that the initial deflection of the heel section28 occurs immediately adjacent the rearward extremity 56 of said heelsection, terminating immediately adjacent the function block 70.Obviously, a greater length or less resilient function block 70 reducesthe lever arm of the heel section 28 of the foot portion 12 andcorrespondingly reduces the modulus of deflection of said ankle section,while a smaller length or more resilient function block 70 increases thelever arm and correspondingly increases the deflection of the heelsection 28 under load. The length of the second function block 72likewise affects the lever arm and deflection of the toe section 24 ofthe foot portion 12

The toe section 24 and heel section 28 can be provided in differentlengths to correspond to the size of the foot of the wearer of theprosthesis 10. When such different lengths are provided, correspondingreduction or increase in the number of laminae and thickness of taper ofthe respective toe section 24 and heel section 28 can be made to providefor the proper flexure of said toe and ankle sections. It should also benoted that, even with the shortest heel section 28, the rearwardextremity 56 thereof projects beyond the rearward surface 58 of theankle portion 14. Consequently, the stabilizing and stress-absorptioncharacteristics of the heel section 28 of the prosthesis 10 are alwaysmaintained.

In an alternative embodiment, shown in FIGS. 5-8, a toe section 82 canbe incorporated into an ankle portion 80, and a heel portion 84 can bepermanently or detachably associated therewith to practice certainaspects of the invention. Except for the toe section 82 being attachedto the ankle portion 80 rather than the heel portion 84, the alternativeembodiment of FIGS. 5-8 is constructed and functions similarly to thepreferred embodiment described above. An auxiliary ankle member 86,similar in configuration and function to ankle member 50 in thepreferred embodiment, may be utilized to achieve the benefits associatedwith ankle member 50 in the preferred embodiment. FIGS. 5-8 further showan alternative embodiment of a coupling 90 suitable for joining theankle portion 80, the auxiliary ankle member 86, and the pylon 30 inoperative engagement. Those skilled in the art will understand that manyalternative embodiments of the coupling can be constructed and practicedinterchangeably in connection with the many alternative embodiments ofthe rest of the invention.

The ankle portion 80 of the alternative embodiment of the prosthesisincludes a substantially rigid attachment section 92, a curvilinearankle section 94, an arch section 96 and a toe section 82. The sections92, 94, 96 and 82 of the ankle portion 80 are formed integrally with oneanother and simultaneously by the incorporation of a plurality oflaminae embedded in a hardened, flexible polymer.

The attachment section 92 incorporates two centrally-located openings88, FIG. 8. The attachment section 92 is substantially rigid and capableof sustaining torsional, impact and other loads impressed thereupon bythe ankle portion 80 and heel portion 84 of the prosthesis. In addition,the inherent rigidity of the attachment section 92 causes the effectivetransmission of the aforesaid loads imposed thereupon to a suitableancillary prosthetic pylon 30, by bolt and nut combinations 98 assembledthrough openings 88 to a pylon coupling 90. A screw 100 or othersuitable attachment means secures the ancillary pylon 30 in the coupling90.

In the particular alternative embodiment of FIGS. 5-8, the auxiliaryankle 86 is mounted between coupling 90 and ankle portion 80, and issecured in operative relationship with the ankle portion ankle section94 through the us of centrally-located openings in an attachment section102 of the ankle member 86, which openings are substantially alignedwith openings 88 of the ankle portion attachment section 92. Bolt andnut combinations 98 retain the various components in the aforesaidoperative relationship. Alternative embodiments would include securingthe auxiliary ankle 86 to the rearward surface of the attachment section92 a described above for the preferred embodiment.

In this alternative embodiment, bolt and nut combinations 104 similar tothe combinations 16 in the preferred embodiment, in conjunction with theload-distributing metallic plates 106 similar to the plates 17 in thepreferred embodiment, serve to secure the heel portion 84 in operativerelationship with the ankle portion 80 of the prosthesis, as best shownin FIGS. 5-6 of the drawings. The aforesaid mode of affixationfacilitates the assembly or dismounting of selected heel portions 84 inoperative relationship with selected ankle portions 80, thus permittinga wide range of different sizes and stress load response characteristicsto be related to each other to accomplish the optimum functionalcorrespondence between the ankle and heel portions 80 and 84.

It will, of course, be obvious to those skilled in the art that, withrespect to any embodiment of the invention, the fibrous reinforcementsin the form of laminae plies encapsulated in the prosthesis may be fayedor tapered to accomplish a gradual transition as the number of plies isreduced in any area of the foot or ankle portions.

Moreover, if a relatively lightweight individual partakes in sports orother activities which subject the prosthesis 10 to greater loads, anankle or foot portion 14 or 12 will be fitted which will accommodate forthose greater loads.

The ankle section 20 of the ankle portion 1 deflects under load and theauxiliary ankle member 50 similarly deflects. Additionally, the toe andheel sections 24 and 28 of the foot portion 12 deflect under such load.Therefore, when subjected to vertical compression loads, the anklesection 20, the auxiliary ankle member 50, and the toe and heel sections24 and 28 absorb such loads.

Consequently, there is no stress concentration, either in the impactphase when the adjacent surface is initially contacted by the wearer ofthe prosthesis 10, or when return of the accumulated forces stored inthe prosthesis 10 is accomplished.

The curvature of the toe section 24 provides for maximum accommodationof said section during surface contact in both the impact and deliveryphases of the prosthesis 10. Similar considerations apply to thecurvature of the heel section 28 of the foot portion 12 of theprosthesis 10. It will be noted that the arcuate, parabolic curvaturesof the toe and heel sections 24 and 28 of the foot portion 12 providefor relatively extended lever arms which achieve stability and, also,stress storage and stress reaction.

The preferred method of manufacturing the foot and ankle portions 12 and14 and the auxiliary ankle member 50 of the prosthesis 10 is by athermosetting molding process including the utilization of molds havingproperly shaped and sized cavities. The cavities are designed to receivethe requisite number of laminates and the proper volume of polymer.

Unlike prior art unitary devices, the fitting of the prosthesis 10involves the judicious adjustment of the prosthesis by the propercombination of foot and ankle portions 12 and 14 and auxiliary anklemember 50, respectively. It also involves the selection of the properlydesigned ancillary pylon 30 which can be secured by means of thecoupling 32 to the attachment section 18 of the ankle portion 14. Onlywhen the proper correlation between the foot portion 12, ankle portion14, auxiliary ankle member 50, and ancillary pylon 30 has beenaccomplished, can the cosmetic shroud, not shown, be installed upon theassembled, respective portions of the prosthesis 10.

By the prosthesis of my invention I provide a foot which can becarefully matched to the weight, stride and physical characteristics ofthe wearer. This is accomplished by carefully balancing the respectivephysical characteristics of the foot portion 12, the ankle portion 14,the auxiliary ankle member 50, and the various sections thereof.

Moreover, the assembled prosthesis is far lighter in weight than priorart prostheses since the inherent design and structure of theprosthesis, the materials used and the careful calculation of stressfactors of the components of the prosthesis permit fine-tuning of theprosthesis to the needs of the wearer thereof.

I claim:
 1. In a prosthetic foot, the combination of: an ankle portionincorporating upper and lower attachment sections and an elongatedintermediate curvilinear ankle section capable of providing energystorage and release during utilization of said foot; a foot portionincluding an arch section and toe and heel sections, said toe sectionextending substantially forward of a forward termination point of saidankle portion; and attachment means for securing said ankle and footportions in operative relationship with each other.
 2. In a prostheticfoot, the combination of: an ankle portion incorporating upper and lowerattachment sections and an elongated intermediate curvilinear anklesection capable of providing energy storage and release duringutilization of said foot; a foot portion including an arch section andtoe and heel sections, said toe section extending substantially forwardof a forward termination point of said ankle portion; and attachmentmeans for securing said ankle and foot portions in operativerelationship with each other, in which said ankle portion is demountablyattached by said attachment means to said foot portion to permit ankleportions having different spring rates to be secured to said footportion of said foot.
 3. The prosthetic foot of claim 2 in which saidankle portion has an associated auxiliary spring ankle member abuttingsaid curvilinear ankle section and secured in operative relationshiptherewith.
 4. In a prosthetic foot, the combination of: an ankle portionincorporating upper and lower attachment sections and an elongatedintermediate curvilinear ankle section; a foot portion including an archsection and toe and heel sections, said toe section extendingsubstantially forward of a forward termination point of said ankleportion; and attachment means for securing said ankle and foot portionsin operative relationship with each other, in which said ankle portionhas an associated auxiliary spring ankle member abutting saidcurvilinear ankle section and secured in operative relationshiptherewith.
 5. The prosthetic foot of claim 1 or claim 2 or claim 4 orclaim 3 in which a resilient spring member is inserted between anintersecting underside of said lower attachment section of said ankleportion and an upper surface of said foot portion.
 6. The prostheticfoot of claim 1 or claim 2 or claim 4 or claim 3 in which said footportion is fabricated from superimposed laminates maintained inoperative relationship by an encapsulating polymer and said toe, archand heel sections of said foot portion are susceptible to bending stressdetermined by the thickness of the laminates in the respective toe, archand heel sections of said foot portion.
 7. The foot of claim 1 or claim2 or claim 4 or claim 3 in which said ankle portion is fabricated fromsuperimposed laminates encapsulated in a polymer and capable of springstress response as ankle loads are imposed thereupon during theutilization of said foot.
 8. The prosthetic foot of claim 1 or claim 2or claim 4 or claim 3 in which said upper attachment section includes anupwardly extending section having forward and rearward surfaces.
 9. In aprosthetic foot, the combination of: an ankle portion incorporatingupper and lower attachment sections and an elongated intermediatecurvilinear ankle section capable of providing energy storage andrelease during utilization of said foot; a foot portion including anarch section and toe and heel sections, said toe section extendingsubstantially forward of a forward termination point of said ankleportion; and attachment means for securing said ankle and foot portionstogether, said foot portion being attached to said ankle portionintermediate said toe and heel sections.
 10. In a prosthetic foot, thecombination of: an ankle portion incorporating upper and lowerattachment sections and an elongated intermediate curvilinear anklesection capable of providing energy storage and release duringutilization of said foot; a foot portion including an arch section andtoe and heel sections; and attachment means for securing said ankle andfoot portions together, said foot portion being attached to said ankleportion intermediate said toe and heel sections, in which said ankleportion is demountably attached to said foot portion to permit ankleportions having different spring rates to be secured to said footportion of said foot.
 11. In a prosthetic foot, the combination of: anankle portion incorporating upper and lower attachment sections and anelongated intermediate curvilinear ankle section; a foot portionincluding an arch section and toe and heel sections, said toe sectionextending substantially forward of a forward termination point of saidankle portion; and attachment means for securing said ankle and footportions together, said foot portion being attached to said ankleportion intermediate said toe and heel sections, in which a resilientspring member is inserted between the intersecting underside of saidlower attachment section of said ankle portion and the upper surface ofsaid foot portion.
 12. In a prosthetic foot, the combination of: anankle portion incorporating upper and lower attachment sections and anintermediate curvilinear ankle section capable of providing energystorage and release during utilization of said foot; a foot portionincluding an arch section and toe and heel sections; and attachmentmeans for securing said ankle and foot portions together, said footportion being attached to said ankle portion intermediate said toe andheel sections, in which said ankle portion is demountably attached tosaid foot portion to permit ankle portions having different spring ratesto be secured to said foot portion of said foot, in which a resilientspring member is inserted between the intersecting underside of saidlower attachment section of said ankle portion and the upper surface ofsaid foot portion.
 13. The prosthetic foot of claim 9 or claim 10 orclaim 11 or claim 12 in which said foot portion is fabricated fromsuperimposed laminates maintained in operative relationship by anencapsulating polymer and said toe, arch and heel sections of said footportion are susceptible to bending stress determined by the thickness ofthe laminates in the respective toe, arch and heel sections of said footportion.
 14. The foot of claim 9 or claim 10 or claim 11 or claim 12 inwhich said ankle portion is fabricated from superimposed laminatesencapsulated in a polymer and capable of spring stress response as ankleloads are imposed thereupon during the utilization of said foot.
 15. Theprosthetic foot of claim 9 or claim 10 or claim 11 or claim 12 in whichsaid ankle portion has an associated auxiliary spring ankle memberabutting said curvilinear ankle section and secured in operativerelationship therewith.
 16. The prosthetic foot of claim 9 or claim 10or claim 11 or claim 12 in which said upper attachment section includesan upwardly extending section having forward and rearward surfaces. 17.In a prosthetic foot, the combination of: an ankle portion having anattachment section; a foot portion having toe, arch and heel sections,said toe section extending substantially forward of a forwardtermination point of said ankle portion; and attachment means forconnecting said ankle and foot portions to each other, in which saidankle and foot portions are fabricated from superimposed laminatesmaintained in operative relationship by an encapsulating polymer. 18.The prosthetic foot of claim 17 in which said ankle portion has anassociated auxiliary spring ankle member abutting said ankle portion andsecured in operative relationship therewith.
 19. The prosthetic foot ofclaim 17 in which said attachment section includes an upwardly extendingsection having forward and rearward surfaces.